Mutational analysis of key genes in patients from the Kazakh population with early onset of breast cancer.

Abstract

e13038 Background: Breast cancer (BC) represents the most common malignancy and has the highest mortality among women, both in the world and in Kazakhstan. Approximately 20-30% of cases of hereditary BC are caused by presence of BRCA1/2 genes defects. Also, there are additional genes which can increase the risk of BC and they are still under study.The aim of this study was to identify new, detectable and objective markers of key cancer genes by next-generation sequencing (NGS) of young BC patients. Methods: Blood was collected from 129 BC patients (average age 34.87±5.587). DNAs were extracted using GeneJET Genomic DNA Purification Kit. NGS was done on the MiSeq platform using TruSightCancer Kit. NGS data were analyzed by the MiSeq Reporter v. 2.4 software. Variant annotation and interpretation was done by Variant Studio 3.0 software. Results: We perform the NGS and did the detailed bioinformatics analysis of sequences of 16 key genes of BC (BRCA1/BRCA2, BRIP1, ATM, CDH1, CHEK2, NBN, NF1, PALB2, STK11, TP53, RAD51C, RAD51D, BARD1, MUTYH and FANCC). At all 3016 variants were detected, 1080 (35.8%) out of which were missense; 1494 (49.5%) synonymous; 17 (0.6%) frameshifts; 2 (0.06%) inframe deletions, 8 (0.3%) stop gained; 4 (0.1%) splice variant, 411 (13.6%) intron or non-coding variants. We identified 24 pathogenic and likely pathogenic mutations in 31 patients (24% of all patient cohort), 3 mutations are novel. All mutations were in heterozygous state and were rare or had frequency data not available (NA) in 1000G, ESP6500and ExAC databases. Analysis of mutation type revealed 17 frameshift mutations, 2 missense mutations, 8 stop gained mutations, 4 mutations involving uncorrected splicing. Out of the 31 pathogenic and likely pathogenic variants, were detected 14 in BRCA1, 9 in BRCA2, 4 in TP53 genes, 3 in PALB2 and 1 in NBN. (BRCA2: c.6468_6469delTC, c.7567_7568delCT, c.9976A > T, c.8174G > A, c.2442delC, c.2808_2811delACAA, c.9253delA, c.9409dupA and c.6058G > T; BRCA1: c.2498delT, c.5224C > T, c.3020C > G, c.3352C > T, c.5530+1G > A, c.5341-2delA and BRCA1-c.5329dupC in 6 cases; NBN: c.657_661delACAAA; PALB2: c.172_175delTTGT, c.1034T > G and c.18_22delGAAGC; TP53- c.156dupA, c.1024C > T, c.844C > T and c.584T > C). The most frequent genes were BRCA1 (45%) and BRCA2 (29%). Conclusions: The study focused on identifying mutation profile of early onset BC using NGS. Clinically significant variants was detected which are promising biomarkers for the successful diagnosis and therapy of BC at women in reproductive age.